1. Field of the Invention
This invention relates to power rectifiers for converting AC power signals to DC and, more particularly, to poly-phase rectification circuits employing a plurality of rectifiers.
2. Discussion
Power rectifiers are used in a wide variety of power applications. Generally such devices apply a single AC power signal to a single rectifier for rectifying the signal, thereby converting the alternating current (AC) signal to direct current (DC). When a high DC power output is required, poly-phase rectifier circuits have been used. Poly-phase rectification circuits typically use standard multi-phase rectifiers, each rectifier being driven by a separate AC source. These devices are constructed such that the rectified DC output signals obtained from the plurality of rectifiers are summed and provided to a load. This kind of rectification circuit permits each rectifier to conduct for a desired phase of the AC cycle, resulting in a smaller ripple effect on the DC output signal.
These rectifier configurations, however, present a very large variation in reactance as they switch between conducting and non-conducting states. This variation can adversely affect the efficiency and general performance of resonant Radio Frequency (RF) power sources. At very high frequencies it is more difficult to make rectifiers handle a lot of current because inevitably they switch loads much faster. Furthermore, with large amounts of current it is difficult to get a rectifier to switch fast enough to enable it to operate at very high frequencies. Thus, in general, the more current flowing through a rectifier, the less efficient it is. Therefore, it is desirable to have a more efficient rectification circuit that is capable of handling very high frequency signals as well as very large power signals.